Land use changes have contributed significantly to increase the concentration of
greenhouse gases in the atmosphere, especially carbon dioxide, whose emissions have
grown since 1970 by 80%. These changes cause an alteration of soil inducing an impact on
the global carbon cycle that accelerates the soil organic matter decomposition rates
generating CO2 fluxes to the atmosphere.
A process recommended by the Intergovernmental Panel on Climate Change (IPCC), and
recognized in the Kyoto Protocol, is the carbon sequestration that implies removal of
atmospheric CO2 by plants and storage as soil organic matter. In order to implant this
practice in a particular ecosystem, studies are necessary to understand the factors that
govern soil respiration and the impact of different land uses on CO2 emissions. In this study,
it was studied 4 different types of land uses representative of semiarid rainfed Aragón: a
cropping system of barley under no-tillage (NT), an abandoned agricultural plowed field
(AC), an abandoned uncultivated field (AU) and a forest area (FR). The objective of the
present study was to evaluate the respiration rates, the environmental factors that
influence these rates and to propose land use changes to mitigate CO2 emissions.
Additionally, it is included a section to explore the response of soil respiration to nitrogen
fertilization (mineral and organic) in a barley system.
In the study of land uses, the obtained results in situ as well as in laboratory have shown
the highest soil respiration in AC and the lowest in NT y FR. Thus, one of the main
conclusions is that the suppression of tillage and the fallow period, and the conversion from
abandoned and marginal soils to forest areas or crops are carbon sequestration practices in
this ecosystem.
In the study of nitrogen fertilization, there was no change in soil respiration rates after
application of mineral nitrogen. In contrast, soil fertilized with manure showed peaks in CO2
emissions during the hours following the addition, mainly due to the high content of labile
carbon of the manure.